In many telecommunication systems, communications networks are used to enable the transport of messages among several interacting spatially-separated devices or network nodes. Network types may be classified by different aspects. In one example, the geographic scope of the network could be over a wide area, a metropolitan area, a local area, or a personal area, and the corresponding networks would be designated as wide area network (WAN), metropolitan area network (MAN), local area network (LAN), or personal area network (PAN). Networks may also be distinguished by the switching or routing technique used to interconnect the various network nodes and devices (e.g. circuit switching vs. packet switching), in the type of physical media employed for transmission (e.g. wired vs. wireless), or in the set of communication protocols used (e.g. Internet protocol suite, SONET (Synchronous Optical Networking), Asynchronous Transfer Mode (ATM) Ethernet, etc.).
One important characteristic of communications networks is the choice of wired or wireless transmission media among the constituents of the network. In the case of wired networks, tangible physical media such as copper wire, coaxial cable, waveguide, fiber optic cable, etc. are employed to propagate guided electromagnetic waveforms which convey message traffic over some distance. Wired networks are typically static configurations and are often favored for interconnection of fixed network elements or for bulk data transfer. For example, fiber optic cables are often the preferred transmission media for very high throughput transport applications over long distances between large network hubs, such as bulk data transport across or between continents over the Earth's surface.
On the other hand, wireless networks are often preferred when the network elements are mobile with dynamic connectivity needs or if the network architecture is formed in an ad hoc, rather than fixed, topology. Wireless networks employ intangible physical media in an unguided propagation mode using electromagnetic waves in the radio, microwave, infrared, optical, etc. frequency bands. Wireless networks have the distinct advantage of facilitating user mobility and rapid field deployment compared to fixed wired networks. However, usage of wireless propagation requires significant active resource management among the network users and high levels of mutual coordination and cooperation for compatible spectrum utilization.